The relevant prior art as per French Pat. No. 73 45204 enhances the transmission of wanted signals and blocks spurious signals by means of a T-junction or a coaxial line trap based upon the principle of filtering by transforming the impedance of a quarter-wave line.
Accordingly, a quarter-wave line terminated at one end by a short circuit or an open circuit returns to the other end an infinite impedance or zero impedance, respectively. A classic example of such a circuit using coaxial lines is shown in FIG. 1, in which coaxial input plug 1 and output plug 2 for the operating signal are disposed in a T-junction wherein each of the lateral arms and the transverse arm are the same length as the quarter wavelength of the design frequency. At the end of the transverse arm, a short circuit 3 across the outside shield of the T and the center conductor returns to the center 4 of the T across the center conductor and the outside shield an impedance which is infinite with respect to the design frequency and practically null with respect to the disturbance frequency signals. Moreover, the lateral arms of the T, have a combined length that is half the wavelength of the operating frequency and impart a coupling between the two coaxial connectors 1 and 2.
However, the T-junction and the trap of the prior art device, made of a rigid metal conductor such as copper, are heavy and bulky as their largest mechanical dimension is equal to a half wavelength.
The device according to the present invention remedies this inconvenience. Said device provides an efficient protection against highpowered spurious signals whilst having more compact dimensions, making it less cumbersome and lighter.